Because PNG is bad at photos. It’s very good compression for stuff with large swaths of simple colors and such, like cartoons or logos, where jpeg compression tends to make big ugly artifacts.
this post was submitted on 26 Dec 2025
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PNG is lossless, but also very inefficient with size if there's anything detailed going on
My camera produces 26 megapixel images, the JPEGs it makes are about 1-2MB. It also creates RAW format files that contain everything about the camera sensor at the point the image was taken, this is the most possible information I can have about the image, and it weighs about 50MB.
A 26 megapixel PNG of a photo takes up about 70MB, and it's got less information in it than the RAW
(Slightly hyperbolic example) If you were scrolling on your phone and it needed to load in images around the 70MB mark, you're not gonna have a remotely snappy experience.
the real reason is most people don’t know anything about file formats and just know that jpg is a picture
Ubiquity, mostly. And because despite not having lossless encoding, JPEGs can be so huge that even industry pros don’t care.
Conversely, JPEG 2000 and JPEG XL never caught on, so it’s not getting any better.
PNG was always good, and I liked using it too for a long time, but these days I just save things as very large JPEGs. I was also disappointed that animated PNGs never became a thing despite being developed.
HEIC/HEIF is the codec/format to watch now.
I thought JPEG XL was possibly about to make a second entrance with Google pivoting recently? Let's hope this is the case.